Apparatus for trimming grinding wheels



Jan. 24, 1967 B. F. BREGI ET AL 3,299,578

APPARATUS FOR TRIMMING GRINDING WHEELS Filed Aug. 17, 1964 FIG. I

-, 1 .mvENTORs l p 32 BENJAMlN F. BREGI- DONALD E BUSH BY EDWARDKRYGIEB/ 4% 7 9/ 14am ATTORNEYS United States Patent 3,299,578 APPARATUSFOR TRIMMING GRINDING WHEELS Benjamin F. Bregi, Grosse Pointe Shores,and Donald P.

Bush and Edward Z. Krygier, Royal ()ak, Mich, assignors to NationalBreach & Machine Company, Detroit, Mich., a corporation of MichiganFiled Aug. 17, 1964, Ser. No. 389,879 27 Claims. (Cl. 51-5) The presentinvention relates to apparatus for trimming grinding wheels.

It is an object of the present invention to provide a trimmer for agrinding wheel in which the path of the trimming element is caused tocorrespond substantially exactly to a plurality of paths on a helicoidalsurface to be ground by the wheel.

It is a further object of the present invention to provide a trimmer fora grinding wheel which comprises a template having a three-dimensionallycurved guide surface, means for mounting said template with said guidesurface confronting a grinding surface located at the side adjacent theedge of the wheel, a trimmer device movable in a multiplicity ofdifferent paths generally transversely between the grinding surface ofthe wheel and the guide surface of the template.

It is a further object of the present invention to provide trimmingmechanism as described in the preceding paragraph in which the trimmerdevice comprises a body, an elongated member movable longitudinallythrough said body, said member having a template follower at one end anda wheel trimming element at the other end.

It is a further object of the present invention to provide a grinder asdescribed in the foregoing in which the template and trimmer device areadjustable so as to position the body and the elongated member with theaxis of the elongated member substantially perpendicular to the axis ofthe helicoidal member to be ground by the wheel, or substantiallyparallel to the axis of the wheel.

It is a further object of the present invention to provide a grindercomprising a frame, a slide movable recti linearly on said frame, asupport on said slide for supporting a work piece having a helicoidalsurface thereon for rotation about the axis of the helicoid, a grindingwheel, means mounting the grinding wheel in position adjacent the pathof movement of the work piece, means for driving the grinding wheel inrotation, means for adjusting the grinding wheel about an axisperpendicular to the axis of the grinding wheel and to the axis of thework piece, a template adjustably mounted on said frame for adjustmentinto an operating position, and means for fixing the template in suchadjusted position, said template having a three-dimensionally curvedguide surface confronting a grinding surface at the side of the grindingwheel adjacent an edge thereof, and a trimmer device movable in amultiplicity of different paths transversely between the grindingsurface of the wheel and the guide surface of the template.

Other objects and features of the invention will become apparent as thedescription proceeds, especially When taken in conjunction with theaccompanying drawings, illustrating preferred embodiments of theinvention, wherein:

FIGURE 1 is a simplified perspective view of a grinder incorporating thetrimming mechanism disclosed herein.

FIGURE 2 is a diagrammatic view illustrating the relationship betweenthe grinding surface of a grinding wheel, the helicoidal surface of awork piece, and a template.

FIGURE 3 is a fragmentary enlarged perspective view showing a preferredform of trimming mechanism.

FIGURE 4 is a perspective view of the template.

While the present invention finds its greatest field of utility ingrinding gears or splines, in its broader aspect it is not so limitedand may find utility in forming helicoidal surfaces on any work piece.However, the present disclosure for the most part will be limited to adescription of the invention as applied to a gear grinding machine, andmore particularly, a machine for grinding helical gears.

Reference is made herein to a helicoidal surface and by this expressionthere is intended to delineate a surface such as the flank surface of atooth of a helical gear. While many tooth forms are known, a standardand widely used tooth form is involute. Accordingly, the helicoidalsurface to which reference is made herein may be an involute helicoid;that is, a surface generated by movement of an involute line along ahelical path, the involute line following a base cylinder whose axis isthe axis of the helicoid.

The present invention is particularly applicable to trimming a grindingwheel used in form grinding. In this grinding operation the edge portionof the wheel may be trimmed so as to provide opposed grinding surfacesat opposite sides of the wheel adjacent its periphery, in which case thegrinding wheel may be used in an oncenter relationship and grind twoopposed involute tooth surfaces in an operation in which the gear isadvanced axially and is given a rotation as required by its lead orhelix angle. Preferably however, the form grinding operation is carriedout by trimming only one side portion of the Wheel adjacent an edgethereof so that the wheel may be used in an off-center relationship, asis well understood in the art.

As is well understood, if a spur gear is ground, the edge portion orportions of the grinding wheel may be trimmed to the exactcross-sectional contour of the tooth surface. Thus, where the tooth isof involute form, the side or sides of the grinding wheel adjacent theedge may be trimmed to the exact cross-sectional involute contour of thetooth surface. However, where the grinding operation is carried out on ahelical gear, heel and toe interference results in the formation of atooth surface on the gear which differs materially from the radialcross-section configuration of the active portion of the grinding wheel.Thus, if the radial cross-section of the grinding wheel is the desiredinvolute, the heel and toe interference will result in a tooth formationon the gear which differs from the desired involute shape.

Moreover, it has been found that this variation between the shape of thetooth surface on the gear and the crosssectional shape of the activesurface of the grinding Wheel is a function of wheel diameter so that asthe wheel wears, there must be a continuous change in the shape of thetrimmed area to maintain uniform accurate results on the gear.

In accordance with the present invention a trimmer is provided whichcauses the trimming element or diamond thereof to move relative to thegrinding wheel so as to trace out a surface which is identical with thehelicoidal surface of the workpiece. Thus, where heel and toeinterference would result, the grinding wheel is trimmed to eliminatethe material which would cause such interference. As a result, thegrinding wheel is automatically trimmed by a simple operation to acontour required to produce the required helicoidal surface on the Workpiece.

Referring to FIGURE 1 there is shown a gear grinder comprising a frame10 on which a slide or table 12 is mounted for reciprocationlongitudinally of the frame in rectilinear ways indicated at 14.Intermediate the ends of the frame and at one side thereof is a column16 which is mounted for angular adjustment about a vertical axis byconventional means (not shown), the vertical axis extendingsubstantially centrally through the grinding wheel W. The wheel W ismounted on a slide 18 capable of verticle adjustment by suitable meanssuch for example as the hand wheel 24 and is adapted to be driven inrotation at grinding speeds by a motor mounted within the column 16.Mounted on the table 12 is a headstock 22 which includes conventionalindexing mechanism (not shown) and which is adapted to receive an arboror the shaft 24- of a helical Work gear G, the other end of the arbor orshaft being mounted in a tail-stock 26'.

In order to provide for helical advance of the gear G as the table ismoved to cause the gear to move back and forth below the grinding wheelW, suitable mechanism is provide-d which may take the form of a lead bar28 coupled to the shaft or arbor 24 and movable through a fixed nut 30so that rotation is imparted to the gear G in timed relation to itsaxial advance. It will be appreciated that the column 16 is angularlyadjusted to cause the grinding wheel to occupy the appropriate inclinedplane in accordance with the helix angle of the gear G.

The trimming mechanism is indicated generally in FIGURE 1 and comprisesa template support bracket 32 fixed to the frame 10, and a trimmerdevice carried by the table or slide 12, as will subsequently bedescribed in detail.

Before referring to the detailed trimming mechanism, reference is madeto FIGURE 2. In this figure there is shown a portion of a grinding wheelW, the grinding surface of which is indicated at 36 and which in thisinstance is of substantially involute radial cross-section. The grindingwheel is capable of grinding the surface 38 of the tooth 40 of a gear asthe gear is moved parallel to its axis and is rotated in accordance withits helix angle. During this operation of course, the grinding wheelremains in a fixed position and is driven in rotation at grindingspeeds.

In FIGURE 2 there is illustrated a template support plate 42 which isangularly adjustable about a vertical axis, the angular setting of theplate being shown by the indicia 44 in association with a gauge mark 46on the template carrier 48. A template block 49 has at the left sidethereof as seen in this figure, a guide surface 50 which isthree-dimensionally curved to conform to the threedimensional curvatureof the helicoidal surface of the gear tooth 40. Due to the "fact thatthe helicoidal tooth of a gear is of different height due to wrap-aroundon the gear, the guide surface of the template will be shapedcorrespondingly. If with the elements illustrated in FIG- URE 2 in therelationship shown, a trimmer were moved back and forth in amultiplicity of paths conforming to the tooth profile or flank surfaceof the tooth 40, it will be apparent that the grinding wheel will betrimmed so as to eliminate the heel and toe interference which haspreviously been referred to.

Mechanism for accomplishing the foregoing is illustrated in detail inFIGURE 3, where the template block 49 is shown :as carried by the plate42, which in turn is adjusted to the required position on the templatecarrier 48. The carrier 48 is positioned at a required height above thebracket 32 by a riser 52. It will be observed that the bracket 32 isprovided with an elongated T-slot 54 so that the posit-ion of the riser52 and carrier 48, and hence the template 49, may be adjusted as desiredwith reference to the location of the grinding wheel W. However, it isimportant to note that in use during a trimming operation the template49 remains in a fixed position relative to the grinding wheel.

As pointed out previously, the guide surface 50 of the template conformsto the profile or flank surface of the tooth 40. Thus, in the usual casewhere the tooth is an involute tooth of a helical gear, the guidesurface of the template is an involute helicoid.

Intermediate the wheel W and the template 49 there is provided thetrimmer device indicated generally at 34, which comprises a support 56adjustable longitudinally of the T-slot 58 provided in the table orslide 12. A

height riser 60 is illustrated as positioned atop the support 56, andabove the riser 64) is a trimmer block 62 having a pair of laterallyextending ears 64 between which is mounted for angular adjustment atrimmer base 66. The angular adjustment of the trimmer base 66 is shownby indicia 66a. The block 62 is also adjustable relative to the slide 56and riser 60 about a vertical axis provided by a pivot support, theupper end of which is indicated at 67. The trimmer device includes abody 68 which is connected to the trimmer base 66 by a pair of parallellinks 70, the links being pivoted to the base 66 as indicated at 72a andto the body 68 as indicated at 74. If desired, a manual operating knobmay be connected to the extension of one pivot shaft 7212, or ifdesired, a motor may be connected to the shaft 72b to impart back andforth oscillation of the body 68.

Located slidably within the body 68 is an elongated member 76 providedintermediate its ends with a spring seat 78 and having a compressionspring 80 connected thereto which biases the member toward the template4?. At the end thereof adjacent the grinding wheel W the elongatedmember 76 is provided with a trimmer element 82 which conventionallytakes the form of 21 diamond. At its opposite end the elongated member76 is provided with a follower element 84 which is movable over thethree-dimensionally curved guide surface 50 of the template.

In use, in order to trim the grinding wheel, the table or slide 12 istraversed to a position in which the gear G is moved away from thegrinding wheel W and the trimmer device 34 is moved into positionbetween the grinding wheel W and the template 49. At this time in orderto trim the wheel to the required configuration, the body 68 is causedto move back and forth repeatedly as con- 7 strained by the parallellinks 70. This causes the body 68 to move in a curved path which mayapproximate the transverse curvature of the grinding surface of thewheel W. However, the follower element 84 at this time is maintained incontact with the guide surface of the template and accordingly, thetrimming element 82 moves in corresponding paths. If at this time thetrimmer is movable only in a plane radial of the grinding wheel, it isapparent that the grinding wheel will be trimmed to an involutecross-section but this will not eliminate the problem presented by heeland toe interference. Accordingly, in addition to the movement in avertical plane occasioned by oscillation of the body 68 as constrainedby the links 70, an additional movement is imparted to the body byappropriate movement of the table 12. Thus, in practice the trimmingoperation may be carried out by causing the table 12 to traverse thetrimming mechanism slowly past the grinding wheel while the body 68 ismoved repeatedly in the vertical plane. The rate of movement of thetable is of course limited because it is essential for the trimmingelement to make a multiplicity of passes so as to trim the grindingwheel in such a wey as to eliminate heel and toe interference. Theresult of the foregoing is that the trimming element is caused to movein a multiplicity of closely spaced substantially but not exactlyparallel paths. In fact, alternate paths during movement of the trimmingelement in an upper direction are substantially parallel as are thealternate paths traced during downward movement of the trimming element.

The mechanism may be employed with the template 49 and the trimmerdevice 34 positioned so that the elongated member 76 occupies a planeparallel to the axis of the grinding wheel. Alternatively, byappropriate adjustment of the parts, the longitudinal axis of the member76 may be substantially perpendicular to the axis of the work gear.

Similarly, while in FIGURE 3 the axis of the elongated member 76 isillustrated as substantially horizontal, it will be readily apparentthat by an increase for example in the height of the riser 60 and by areduction in height of the riser 52, the axis of the elongated member 76may be caused to incline inwardly and to the right so as to cause theelongated member 76 to extend more nearly perpendicular to the grindingsurface of the wheel W.

While the foregoing preferred embodiment of the present invention isvery simple and calls for the use of a template of exactly the sameshape and size as a portion of the helicoidal surface of a gear tooth,it is within the scope of the present invention to provide a templatewhich may be several times larger and in which the trimmer deviceintermediate the template and the edge of the grinding wheel is in theform of pantograph mechanism, as is well understood in the art.Accordingly, the template herein is defined as substantiallygeometrically similar to the helicoidal surface to be ground on the workpiece, and by this expression geometrically similar is meant a surfacewhich is substantially identical in shape but which may be quitedifferent in size.

A very important advantage of the present invention is that the trimmingmechanism automatically imparts the required configuration to thegrinding wheel irrespective of the diameter of the wheel. Thus, as thewheel is worn down in use, and is repeatedly trimmed, the contour of thewheel changes but it is unnecessary to take the change in contour of thewheel in to account. The contour is always exactly that required toeliminate the heel and toe interference and to produce the requiredcontour on the helicoidal surface of the work piece. This of course isalways accomplished using the same template 49 which has the requiredhelicoidal surface or a geometrically similar surface thereto.

The drawings and the foregoing specification constitute a description ofthe improved apparatus for trimming grinding wheels in such full, clear,concise and exact terms as to enable any person skilled in the art topractice the invention, the scope of which is indicated by the appendedclaims.

What we claim as our invention is:

1. A trimmer for a grinding wheel for use in grinding helicoidal forms,comprising a template having a threedimensionally curved guide surfacegeometrically similar to a helicoidal surface on a work piece, means forpositioning the template in fixed position adjacent the wheel and inparallelism with the position occupied by the work piece surface duringgrinding, a trimmer device comprising a trimming element in position totraverse a side portion adjacent the edge of the grinding wheel, andfollower mechanism connected to the trimming element and including afollower element engageable with the guide surface of the template andeffective to move the trimming element in accordance with movementimparted to the follower element by movement over the guide surface ofsaid template, means for moving said trimmer device between saidtemplate and wheel to cause said follower element effectively to coveran area of the guide surface and to thereby cause said trimming elementto trace out a substantial area intersecting the grinding portion of thewheel which is geometrically similar to the guide surface of saidtemplate.

2. A trimmer as described in claim 1 in which the guide surface of saidtemplate is substantially identical to the helicoidal surface to beground on the work piece.

3. A trimmer as described in claim 2 in which said trimmer devicecomprises a carrier body, an elongated member movable longitudinally insaid body, said trimming and follower elements being located at oppositeends of said body.

4. A trimmer as described in claim 3, said body being movable in twodifferent directions both substantially normal to the axis of saidmember.

5. A trimmer as described in claim 4 in which said template and trimmerdevice are located such that the axis of said member is substantiallyparallel to the axis of said wheel.

6. A trimmer as described in claim 4 in which said template and trimmerdevice are located such that the axis of said member is substantiallyperpendicular to the axis of the helicoidal surface of the work piece.

7. A trimmer for a grinding wheel comprising a template having athree-dimensionally curved guide surface adapted to be positioned toconfront a side portion adjacent the edge of a grinding wheel, and atrimmer device having a trimming element and a follower element, meansinterconnecting said elements to cause said trimming element to move andtrace a three-dimensionally curved surface Which is geometricallysimilar to the guide surface of the template, and means for moving saiddevice to move said trimming and follower elements in a multiplicity ofadjacent paths which in total cause the trimming element to trace outthe required surface.

8. A trimmer as described in claim 7 in which said trimmer devicecomprises a carrier body, an elongated member movable longitudinally insaid body, said trimming and follower elements being located at oppositeends of said body.

9. A trimmer as described in claim 8, said body being movable in twodifierent directions both substantially normal to the axis of saidmember.

10. A trimmer as described in claim 9 in which said template and trimmerdevice are located such that the axis of said member is substantiallyparallel to the axis of said wheel.

11. A grinder comprising a frame, a slide movable rectilinearly on saidframe, a work support on said slide including means for supporting awork piece having a helicoidal surface for rotation about the axis ofsaid helicoidal surface with its axis of rotation parallel to thedirection of reciprocation, means responsive to movement of said slideto rotate the Work piece, a rotary grinding wheel, means mounting saidwheel on said frame for angular adjustment about an axis perpendicularto and intersecting the axis of said wheel and the axis of rotation of awork piece on said work support, means for driving the wheel inrotation, a template on said frame having a helicoidal guide surfacegeometrically similar to the portion of a helicoidal surface of a workpiece at and adjacent the zone of contact with said wheel, said templatebeing fixed to said frame with its guide surface confronting the workcontacting zone of the wheel, a trimmer device mounted on said slide formovement therewith into and out of a trimming position interposedbetween the guide surface of said template and the work contacting zoneof the wheel, said trimmer device comprising a follower element movableover the guide surface of said template, a trimming element movable intrimming relation relative to the work contacting zone of said wheel,and means connecting said follower and trimming elements to cause saidtrimming element to trace out an area geometrically similar to the guidesurface of said template.

12. A grinder as defined in claim 11 in which said guide surface isoriented in parallelism with the portion of the helicoidal surface of awork piece at the zone of contact with said wheel.

13. A grinder as defined in claim 11 in which said trimming element ismovable repeatedly in generally parallel paths approximately radial ofsaid wheel and is movable transversely of such paths between successivemovements in said paths.

14. A grinder as defined in claim 12 in which the guide surface of saidtemplate is substantially identical to the helicoidal surface to beground on the work piece.

15. A grinder as defined in claim 14 in which said trimmer devicecomprises a carrier body, an elongated member movable longitudinally insaid body, said trimming and follower elements being located at oppositeends of said body.

16. A trimmer as defined in claim 15, said body being movable in twodifferent directions both substantially normal to the axis of saidmember.

17. A trimmer as defined in claim in which said template and trimmerdevice are located such that the axis of said member is substantiallyparallel to the axis of said wheel.

18. A trimmer as defined in claim 15 in which said template and trimmerdevice are located such that the axis of said member is substantiallyperpendicular to the axis of the helicoidal surface of the work piece.

19. A trimmer as defined in claim 11 which comprises means for adjustingsaid template about an axis parallel to the axis of adjustment of saidwheel.

20. A trimmer as defined in claim 11 which comprises means forrelatively adjusting said template and wheel in a plane perpendicular tothe axis of rotation of a work piece on said work support.

21. A grinder comprising a frame, a slide movable horizontally andrectilinearly on said frame, a work support on said slide includingmeans for supporting a work piece having a helicoidal surface forrotation about the axis of said helicoidal surface with its axis ofrotation parallel to the direction of reciprocation, means responsive tomovement of said slide to rotate the work piece, a rotary grindingwheel, means mounting said wheel on said frame in position over a workpiece on said work support for angular adjustment about a vertical axisperpendicular to and intersecting the axis of said wheel and the axis ofrotation of a work piece on said work support, means for driving thewheel in rotation, a template on said frame having a helicoidal guidesurface geometrically similar to the portion of a helicoidal surface ofa work piece at and adjacent the zone of contact with said wheel, saidtemplate being fixed to said frame with its guide surface confrontingthe work contacting zone of the wheel, a trimmer device mounted on saidslide for movement therewith into and out of a trimming positioninterposed betwen the guide surface of said template and the workcontacting zone of the wheel, said trimmer device comprising a followerelement movable over a substantial area of the guide surface of saidtemplate, a trimming element movable in trimming relation relative tothe work contacting zone of said wheel, and means connecting saidfollower and trimming elements to cause said trimming element to traceout an area geometrically similar to the guide surface of said template.

22. A grinder as defined in claim 21 in which the guide surface of saidtemplate is identical with and parallel to the portion of a helicoidalwork piece surface in the zone of contact with said Wheel.

23. A grinder as defined in claim 22 in which said trimmer devicecomprises a carrier body, an elongated member movable longitudinally insaid body, said trimming and follower elements being located at oppositeends of said body.

24. A grinder as defined in claim 23, said body being movable in avertical plane relative to said slide and being movable horizontallywith said frame to trace out a substantial area of three-dimensionallycurved helicoidal surfaces adjacent said wheel.

25. A grinder as defined in claim 23 comprising means mounting saidtemplate on said frame for angular adjustment about a vertical axis.

26. A grinder as defined in claim 22 comprising means for adjusting saidtemplate horizontally on said frame parallel to the path of movement ofsaid slide.

27. A grinder as defined in claim 22 which comprises a carrier, parallellinks connecting said body to said carrier, means for effecting -arelative height adjustment between said wheel and said template, andmeans for angularly adjusting said carrier about an axis parallel to thepath of movement of said slide.

References Cited by the Examiner UNITED STATES PATENTS 1,599,405 9/ 1926Bugbee. 2,151,802 3/1939 Roman -11 3,067,733 12/1962 Pernack 12511ROBERT C. RIORDON, Primary Examiner.

D. G. KELLY, Assistant Examiner.

11. A GRINDER COMPRISING A FRAME, A SLIDE MOVABLE RECTILINEARLY ON SAIDFRAME A WORK SUPPORT ON SAID SLIDE INCLUDING MEANS FOR SUPPORTING A WORKPIECE HAVING A HELICOIDAL SURFACE FOR ROTATION ABOUT THE AXIS OF SAIDHELICOIDAL SURFACE WITH ITS AXIS OF ROTATION PARALLEL TO THE DIRECTIONOF RECIPROCATION, MEANS RESPONSIVE TO MOVEMENT OF SAID SLIDE TO ROTATETHE WORK PIECE, A ROTARY GRINDING WHEEL, MEANS MOUNTING SAID WHEEL ONSAID FRAME FOR ANGULAR ADJUSTMENT ABOUT AN AXIS PERPENDICULAR TO ANDINTERSECTING THE AXIS OF SAID WHEEL AND THE AXIS OF ROTATION OF A WORKPIECE ON SAID WORK SUPPORT, MEANS FOR DRIVING THE WHEEL IN ROTATION, ATEMPLATE ON SAID FRAME HAVING A HELICOIDAL GUIDE SURFACE GEOMETRICALLYSIMILAR TO THE PORTION OF A HELICOIDAL SURFACE OF A WORK PIECE AT ANDADJACENT THE ZONE OF CONTACT WITH SAID WHEEL, SAID TEMPLATE BEING FIXEDTO SAID FRAME WITH ITS GUIDE SURFACE CONFRONTING THE WORK CONTACTINGZONE OF THE WHEEL, A TRIMMER DEVICE MOUNTED ON SAID SLIDE FOR MOVEMENTTHEREWITH INTO AND OUT OF A TRIMMING POSITION INTERPOSED BETWEEN THEGUIDE SURFACE OF SAID TEMPLATE AND THE WORK CONTACTING ZONE OF THEWHEEL, SAID TRIMMER DEVICE COMPRISING A FOLLOWER ELEMENT MOVABLE OVERTHE GUIDE SURFACE OF SAID TEMPLATE, A TRIMMING ELEMENT MOVABLE INTRIMMING RELATION RELATIVE TO THE WORK CONTACTING ZONE OF SAID WHEEL,AND MEANS CONNECTING SAID FOLLOWER AND TRIMMING ELEMENTS TO CAUSE SAIDTRIMMING ELEMENT TO TRACE OUT AN AREA GEOMETRICALLY SIMILAR TO THE GUIDESURFACE OF SAID TEMPLATE.